Yeah, when any of the aforementioned things happen it causes too much CO2 to go into solution with the beer. Then, when starts coming out of solution, (i.e. when the pressure is released) it comes out too quickly causing all of the beer to turn to foam.

As others have mentioned, it is most likely either bottling after incomplete fermentation or an infection.

What I want to add is that you should be very careful around these bottles. Honestly, I would carefully un-cap them all and dump them out. If it continues to ferment, you might have a bunch of bottle bombs on your hand.

The recipe was a very simple extract lager recipe that I had thrown together. I gave it 9 days in the primary at 50*F and then 10 days in the secondary at 45*F. My air stop wasn't bubbling but every few minutes, and visually the beer seemed to be at a complete standstill. I did not take a hydrometer reading. I don't have a ton of experience but to my knowledge it had completed fermenting.

I'm thinking it's a sanitation issue.

I'm not sure if there is a simpler (or more correct) way to sanitize bottles but I sanitized my bottles using a 72 min, added heat wash in my dishwasher. This has always worked for me in the past. Does anyone have a better way to sanitize?

I'm thinking something must have got into the beer itself, because every bottle I have opened has been the same characteristics. I think that I need to spend a little time soaking all my equipment in bleach water and I may need to grab a new Better Bottle just to be safe. Cross your fingers that the beer that is in there now isn't screwed up.

What yeast and how much? Based on your short fermentation schedule, I don't think it was finished. You were fermenting at a low temp, which takes longer. And I don't trust visual signs....I trust my hydrometer.